Experimental parametric study on low-frequency oscillating behaviour of pool fires in a small-scale mechanically-ventilated compartment

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

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Poststack impedance inversion considering the diffractive component of the wavefield

Geophysics ◽

10.1190/geo2018-0661.1 ◽

2020 ◽

Vol 85 (1) ◽

pp. R11-R28 ◽

Cited By ~ 1

Author(s):

Kun Xiang ◽

Evgeny Landa

Keyword(s):

Specular Reflection ◽

Low Frequency ◽

Velocity Model ◽

Forward Modeling ◽

Small Scale ◽

Fracture Detection ◽

Frequency Model ◽

New Approach ◽

Impedance Inversion ◽

Diffraction Imaging

Seismic diffraction waveform energy contains important information about small-scale subsurface elements, and it is complementary to specular reflection information about subsurface properties. Diffraction imaging has been used for fault, pinchout, and fracture detection. Very little research, however, has been carried out taking diffraction into account in the impedance inversion. Usually, in the standard inversion scheme, the input is the migrated data and the assumption is taken that the diffraction energy is optimally focused. This assumption is true only for a perfectly known velocity model and accurate true amplitude migration algorithm, which are rare in practice. We have developed a new approach for impedance inversion, which takes into account diffractive components of the total wavefield and uses the unmigrated input data. Forward modeling, designed for impedance inversion, includes the classical specular reflection plus asymptotic diffraction modeling schemes. The output model is composed of impedance perturbation and the low-frequency model. The impedance perturbation is estimated using the Bayesian approach and remapped to the migrated domain by the kinematic ray tracing. Our method is demonstrated using synthetic and field data in comparison with the standard inversion. Results indicate that inversion with taking into account diffraction can improve the acoustic impedance prediction in the vicinity of local reflector discontinuities.

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A parametric study of the small-scale solar pond (SSSP)

Energy Conversion and Management ◽

10.1016/0196-8904(86)90014-2 ◽

1986 ◽

Vol 26 (3-4) ◽

pp. 337-345 ◽

Cited By ~ 8

Author(s):

W.A. Kamal

Keyword(s):

Parametric Study ◽

Small Scale ◽

Solar Pond

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Parametric study of the small scale linear Fresnel reflector

Renewable Energy ◽

10.1016/j.renene.2017.09.066 ◽

2018 ◽

Vol 116 ◽

pp. 64-74 ◽

Cited By ~ 15

Author(s):

A. Barbón ◽

N. Barbón ◽

L. Bayón ◽

J.A. Sánchez-Rodríguez

Keyword(s):

Parametric Study ◽

Small Scale ◽

Linear Fresnel Reflector

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Internal tide energy flux over a ridge measured by a co-located ocean glider and moored ADCP

10.5194/os-2019-15 ◽

2019 ◽

Author(s):

Rob Hall ◽

Barbara Berx ◽

Gillian Damerell

Keyword(s):

Energy Flux ◽

Large Scale ◽

Low Frequency ◽

Internal Tide ◽

Small Scale ◽

Potential Density ◽

The North ◽

Model Study ◽

Continental Shelves ◽

Alternative Approach

Abstract. Internal tide energy flux is an important diagnostic for the study of energy pathways in the ocean, from large-scale input by the surface tide, to small-scale dissipation by turbulent mixing. Accurate calculation of energy flux requires repeated full-depth measurements of both potential density (ρ) and horizontal current velocity (u) over at least a tidal cycle and over several weeks to resolve the internal spring-neap cycle. Typically, these observations are made using full-depth oceanographic moorings that are vulnerable to being fished-out by commercial trawlers when deployed on continental shelves and slopes. Here we test an alternative approach to minimise these risks, with u measured by a low-frequency ADCP moored near the seabed and ρ measured by an autonomous ocean glider holding station by the ADCP. The method is used to measure the M2 internal tide radiating from the Wyville Thompson Ridge in the North Atlantic. The observed energy flux (4.2 ± 0.2 kW m−1) compares favourably with historic observations and a previous numerical model study. Error in the energy flux calculation due to imperfect co-location of the glider and ADCP is estimated by sub-sampling potential density in an idealised internal tide field along pseudorandomly distributed glider paths. The error is considered acceptable (

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Characterization and Parametric Study of Multilayered IPMC Actuator

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.983.161 ◽

2014 ◽

Vol 983 ◽

pp. 161-165

Author(s):

Muhammad Farid Shaari ◽

Zahurin Samad

Keyword(s):

Parametric Study ◽

Weight Ratio ◽

Small Scale ◽

Metal Composite ◽

Ionic Polymer Metal Composite ◽

End Effector ◽

Ionic Polymer ◽

Actuation Force ◽

Polymer Metal ◽

Robotic Applications

Ionic Polymer-Metal Composite (IPMC) has been utilized as an actuator in several robotic applications such as the actuator for its locomotion and gripper of the end effector. However, due to its low actuation force which is normally less than 10gf (depend on dimension), the application has been limited to small scale robot. Hence, in this research we propose a multilayer structure of IPMC actuator and investigate the actuation force increment. Besides, parametric study was also conducted to determine the force-to-weight ratio and the bending displacement. The obtained results had been compared to single ply IPMC actuator at the same thickness. The result shows that the increment of IPMC layer had increased the actuating force up to 30% for two layers and 40% for three layers. In addition, utilizing multilayered IPMC had reduced the stiffness constraint for thicker IPMC. This finding would be useful in designing stage of a small scale robot that require higher actuation force at a higher bending displacement.

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Modeling and linear analysis of sound generation mechanism in sonic soot blowers

Journal of Vibration and Control ◽

10.1177/1077546319852816 ◽

2019 ◽

Vol 25 (17) ◽

pp. 2305-2315

Author(s):

A. Najafi ◽

M. Asayesh ◽

A. Siami

Keyword(s):

Sound Wave ◽

Parametric Study ◽

Low Frequency ◽

Linear Analysis ◽

Generation Mechanism ◽

Frequency Content ◽

Sound Generation ◽

Governing Equations ◽

High Level ◽

Frequency Sound Wave

Sonic soot blowers (SSBs) are nondestructive tools to prevent ashes and particle build-up on the surfaces of boilers or other similar instruments. For higher performance, sonic soot cleaners should generate a high level-low frequency sound wave. In this article, the sound generation mechanism in these tools has been modeled. Firstly, the governing equations of the diaphragm and the horn and coupling between them are derived. By linearization, a parametric study is performed to find the optimum design points. Based on the eigenvalue analysis, it is shown that the sound generation in sonic soot cleaners is due to instability of the interaction between the diaphragm and the horn. Moreover, it is found that the sound wave frequency is approximately equal to the lowest fundamental frequency of the horn or diaphragm. Finally, the frequency content of an SSB voice is investigated.

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Inductance of Low-Frequency Small-Scale High-Temperature Superconducting Coils

IEEE Transactions on Applied Superconductivity ◽

10.1109/tasc.2019.2897868 ◽

2019 ◽

Vol 29 (5) ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Siwei Chen ◽

Chen Gu ◽

Yi Li ◽

Lingfeng Lai ◽

Timing Qu ◽

...

Keyword(s):

High Temperature ◽

Low Frequency ◽

Small Scale ◽

High Temperature Superconducting ◽

Superconducting Coils

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A Parametric Study on the Immunomodulatory Effects of Electroacupuncture in DNP-KLH Immunized Mice

Evidence-based Complementary and Alternative Medicine ◽

10.1093/ecam/nep166 ◽

2011 ◽

Vol 2011 ◽

pp. 1-5 ◽

Cited By ~ 4

Author(s):

Sun Kwang Kim ◽

Youngseop Lee ◽

Hyunjoo Cho ◽

Sungtae Koo ◽

Sun Mi Choi ◽

...

Keyword(s):

Parametric Study ◽

High Frequency ◽

Low Frequency ◽

Specific Ige ◽

Th2 Cytokines ◽

Immunomodulatory Effects ◽

Frequency Dependent ◽

Total Ige ◽

The Difference

This study was conducted to compare the effects of low frequency electroacupuncture (EA) and high frequency EA at acupoint ST36 on the production of IgE and Th1/Th2 cytokines in BALB/c mice that had been immunized with 2,4-dinitrophenylated keyhole limpet protein (DNP-KLH), as well as to investigate the difference in the immunomodulatory effects exerted by EA stimulations at acupoint ST36 and at a non-acupoint (tail). Female BALB/c mice were divided into seven groups: normal (no treatments), IM (immunization only), ST36-PA (IM + plain acupuncture at ST36), ST36-LEA (IM + low frequency (1 Hz) EA at ST36), ST36-HEA (IM + high frequency (120 Hz) EA at ST36), NA-LEA (IM + low frequency (1 Hz) EA at non-acupoint) and NA-HEA (IM + high frequency (120 Hz) EA at non-acupoint). EA stimulation was performed daily for two weeks, and total IgE, DNP-KLH specific IgE, IL-4 and IFN-γlevels were measured at the end of the experiment. The results of this study showed that the IgE and IL-4 levels were significantly suppressed in the ST36-LEA and ST36-HEA groups, but not in the NA-LEA and NA-HEA groups. However, there was little difference in the immunomodulatory effects observed in the ST36-LEA and ST36-HEA groups. Taken together, these results suggest that EA stimulation-induced immunomodulation is not frequency dependent, but that it is acupoint specific.

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